Ceramic material



March 1, 1932. l w. 1 sco-[T 1,847,102

CERAMIC MATERIAL `Filed July ll, 1928 WALTER JEFFERSON sco'rr, or EnooxErEL 'raro COMPANY, INcoEroEATEnA-or NEW Yonx, N.

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D,'-ILLINOIS, ASSIGNOB T0 WESTERN ELEC- Y Y., A conrom'rroN'or NEW cEEAmc MATERIAL i Application fled July 11,- 1,928. Serial No. 291,948.

This invention relates to ceramic materials and'methods of making the same, and has for its objects the provision of ceramic materials which may be easily molded and which may be converted into articles having high electrical insulating properties, and the rovision of simple, expeditious and e ective methods of making ceramic materials and articles.

In accordance with the general features of the invention as embodied in one specific form thereof, ceramic substances, suchl as talc and clay, and water are mixed in proorm a mass of a thick liquid conground. A temporary binding material, such as paran, dissolved in a suitable solvent is added to the mixtureand thoroughly mixed therein and at the same time the mix' ture is heated to evaporate the solvent. The dry mixture of clay, talc and paraffin is-then milled to produce a tine owder, the mixture Ais moldedto the desired orm and the molded part is heat treated at approximately 2200 F. to remove the paraiiin and to harden vthe ceramic composition. u

` TheA above enumerated and other objects and features of the invention will be apparent from the following detailed description of one embodiment of thev invention taken in conjunction with the accompanying drawings, in which A i Fig. 1 is a cross-sectional view of a telephone transmitter of an usual type including a part composed of a ceramic material made in accordance withfthe invention, and

Fig. 2 is an enlarged perspective view of the part.

In practicingfone method embodying the 'i invention about 7 5 parts of talc and 25 parts of a suitable clay, such as kaolin, are mixed with@ a suiicient quantity of water to form a mass of a thick liquid consistency'and the resulting mass is dried and ground to a line powder, after which the ground material is Asie'ved through a-100 mesh screen. An organic temporary binding agent dissolved in `a suitable solvent isthen added to the dried groundmixtureof talc and kaolin. A suitable solution for this purpose comprises about 16 parts of paraiiin dissolved in a noncombustible solvent, such as carbon-tetrachloride. The solution is thoroughly mixed throughout the mixture of talc and kaolin and the resulting mixture is simultaneously heated to evaporate the carbon-tetrachloride.

' The dry mixture of talc, kaolin and paraffin is then thoroughly milled to reduce the` particlcs to a small size and the resulting mass is screened through a 100 mesh screen.

The finely divided powder produced by the above outlined steps is a very satisfactory molding composition Jfrom 'which ceramic articles may be produced. One satisfactoryI method of employing the molding compositionl is to press a quantity of the powder into thedesired form in a cold mold by mea-ns of a hydraulic press or otherV suitable apparatus, to trim the molded part, if necsary, to remove projecting fins, and to heat the molded part at a high temperature (about 2200 F.) to remove the paraiiin and to harden the ceramic composition.

Since it is diilicult to press a. dry mixture of talc and kaolin into a desired form, and when parts molded rom'these or similar materials are held together during the molding operation 'by a liquid binding agent, such as water,

and warp when the molded parts are heated, a dry, temporary binding agent which is removed when the molded part is subjected. to a high temperature, is employed to hold the talc and kaolin inthe desired form during the firing operation. Parain has proven to be a very satisfactory material to use Jfor this purpose, but other related materials may be used with satisfactory resultsy Y The molding composition described hereinbefore is very suitable for use in the manufacture of so-called barrier rings used in some types of telephone transmitters, and a ring made of this composition is illustrated in the accompanying drawings. In utilizing the composition, a ring 10, such as is shown in Fig. 2 of the drawings, is prepared in accordance` with the method described hereinbefore and is positioned between electrodes 12 and the resulting parts have a great ten- Adency to shrink additional ner circumference of the ring projects into a mass of granular carbon 15 positioned between the electrodes 12 and 13. Due to its position and shape, the barrier ring causes an electric current flowing from one electrode to the other electrode to traverse a path through the central part of the mass of carbon located between the electrodes. The electrical resistance. offered to the passage of the current between the electrodes therefore depends entirely upon the resistance of the car- -bon particles, which in the operation of the transmitter may be rapidly varied because of the movement transmitted to the carbon particles by a diaphragm 16 which iscaused to vibrate by the sound waves entering the transmitter.

Because of the high mechanical strength, high dielectric strength, high insulating resistance at both low and high temperatures, the permanence of the size, shape and electrical properties, and freedom from alteration by atmospheric conditions of ceramic materials' produced by the above described method, barrier rings made from the molding composition described hereinbefore `give results which are equal to or better than similar rings known to the art and have the advantage that they may be cheaply and easily made in the desired shape and size within very close limits.

It is, of course, to be understood that the embodiments of the invention described above are merely useful forms of the invention which illustrate how the invention may be practiced and the scope of the invention is but the invention is scope of the annexed not limitd thereby, limited only. by the claims.

What is claimed is:

1. A method of making ceramic molding compositions which consists in mixing ceramic substances with a solution of paralin, and evaporating the solvent in which the parailin is dissolved.-

2. A method of making ceramic molding compositions which consists in mixing talc and clay with a solution of parailin, and evaporating the solvent in which the paralin is dissolved.

3. A methodl of making ceramic compositions which consists in mixing talc and clay with a solution of parallin in a non-combustible solvent, and evaporating the solvent.

4. A method of making ceramic molding compositions which consist in mixing talc and clay with a solution of paraffin in carbontetrachloride, and evaporating the carbontetrachloride. 5. A method of making ceramic molding compositions which consists in mixing about 7 5 parts talc and 25 parts kaolin with a solution of about 16 part-s paraliin in carbontetrachloride,

an'd evaporating the carbontetrachloride.

materials which consists in mixing talc and clay with a solution of an organic temporary binding agent, evaporating the solvent in which the binding agentis dissolved, molding the resulting mass into the desired form, and heating the molded mass at a temperature sulliciently high to remove the binding agent and to harden the remaining substances.

8. A method of making articles of ceramic material which consists in mixin ceramic substances with a solution of paran in carbon-tetrachloride, evaporating the carbontetrachloride, molding the resulting mass into the desired form, and heating the molded mass-at Ia temperature sutliciently high to remove the binding agent and toharden the ceramic substances.

9. A method of making articles of ceramic materials which consists in mixing talc and clay with a solution of parailin in carbontetrachloride, evaporating the carbon-tetrachloride, molding the resulting mass into the desired form, and heating the molded mass at a temperature sufticiently high to remove the binding agent and to harden the remaining substances.

10. A method of making articles of ceramic materials which consists in mixing about parts talc and 25 parts kaolin with about 16 parts paraHin ydissolved in carbon-tetrachloride and simultaneously evaporating the carbon-tetrachloride, molding the resulting mass into the desired form, and heatinfr the molded mass at a temperature of a out 22000 F. to remove the parailin and to harden the remaining substances.

11. A method of making-a ceramic article' `which comprises mixing a finely divided insulating material with a solution of parafn without the addition of water or of coarse dried mass, mlxmg the ground material with a solution of parain, molding the mixture to a desired form, and firing the resulting article.

In witness whereof, I hereunto subscribe my name this 30th da of June, A; D. 1928.

WALTER JE FERSON SCOTT. 

